Cells dispatch a variety of critical functions via cytoskeletal arrays that are inherently transitory, i.e. structures that assemble in response to specific cues, perform their task, and then disassemble within the space of several minutes. In the proposed studies, we will investigate three such transient cytoskeletal arrays: one based on F-actin and myosin-2 and is involved in cell repair (the wound cytoskeletal array), one that is based on F-actin and myosin-2 and is involved in cell division (the cytokinetic apparatus) and one that is responsible for chromosome separation (the mitotic spindle). For the wound cytoskeletal array, we will test the hypothesis that the contraction powered by F-actin and myosin-2 feeds directly back upon the signaling molecules (the small GTPases, Rho and Cdc42) that direct its formation. We will also test the hypothesis that formation of this array is linked to the cell damage event via exocytosis-dependent lipid remodeling. For the cytokinetic apparatus, we will test the hypothesis that it is generated via a diffusional signal arising from the spindle. We will also test the hypothesis that the same general feedback posited to exist in the wound cytoskeletal array functions in the cytokinetic apparatus. For the mitotic spindle, we will test the hypothesis that a link between the assembly and function of this structure to an unusual motor protein called myosin-10 is mediated by a cell cycle-regulating kinase called wee1. We will also explore a very old question: do actin filaments and myosins work together within the mitotic spindle to control spindle assembly and function? The proposed experiments are designed to bring innovative experimental approaches and ideas to bear on fundamentally important processes. The long term goal is to understand how these and other transient cytoskeletal arrays manage to fulfill their cellular roles with their characteristic speed, precision, and flexibility. PUBLIC HEALTH RELEVANCE: The proposed studies are designed to address three areas that are poorly understood and yet highly important: The first concerns how single cells repair themselves, a process which is at the heart of the muscular dystrophies; The second and third concern basic mechanisms that control cell division, a process which is at the heart of tumorigenesis. This work will provide cellular and molecular insights into these processes which will permit informed design of clinical interventions for these diseases.